The naturally occurring chemotactic factor inactivator present in human serum will be isolated, purified and characterized. The mechanism of its interaction with leukotactic factors will be investigated. The status of the inactivator in the serum of patients with pulmonary emphysema and a deficiency of anti-trypsin will be assessed. These studies will be carried out by protein purification procedures including ion exchange chromatography, electrophoresis and ultracentrifugation, and by immunochemical approaches.